Method for conditioning grain or similar materials



Dec. 12, 1961 5. OHOLM ETAL 3,012,331

METHOD FOR CONDITIONING GRAIN 0R SIMILAR MATERIALS Filed March 28, 19582 Sheets-Sheet 1 FIGI. 5

FIGZ. 25 4 6 FIGB. a

INVENTORSI SVEN WALL I N GUSTAV OHOLM BY WW Dec. 12, 1961 G. OHOLM ETAL,33

METHOD FOR CONDITIONING GRAIN OR SIMILAR MATERIALS Filed March 28, 19582 Sheets-Sheet 2 FIG. 7 F 1 65 66 ,0? 4 4/ 60 i \"Q fl 2 i 5531 A I i: 14.2

INVENTORS SVEN V\ ALL|N GUSTAV OHOLM ATTYS.

atent fhce 3,912,331 Patented Dec. 12, 1 961 3 612 331 METHGD F8 CQIIDKTIGNING GRAlN QR SWEAR EEATERIALS Gustav Gholnr, Bromrna, SvenWallin, Jot-limping,

Sweden, assignors to Alrtiebolaget Svensira Fiakttabrllren, Stockholm,Sweden Filed Mar. 23, 1958, Ser. No. 724,755 Claims priority,application Sweden Mar. 29, 1957 1 Claim. (Cl. 34-10) The presentinvention relates to a method for conditioning grain or similarmaterials conveyed as a layer on a supporting plane, the grain particlesbeing passed and fluidized by a gaseous medium and thereby being firstdried and then cooled during a treatment in two or more steps.

When drying grain and similar materials, which has to be stored afterdrying, it is necessary to reduce the temperature of the dried grain inorder to avoid the damaging of the quality during the storing period.Generally, this cooling of the grain is efiected simultaneously with thedrying of the grain in such a way that during its passage through thelast part of the drying unit, cold outdoor air is blown through thegrain. However, this cooling method has often proved insufiicient, or arelatively long treatment time has been required with a correspondingincrease of the cost for the drying apparatus. Furthermore, it has beenfound that the quicker the drying is performed, the greater part of thetreatment time will be required for the cooling of the grain.

The invention, which has for its object to eliminate this drawback andin the first place to enable a quicker cooling of the dried grain, isbased on the knowledge'that the necessity for a long cooling thnedepends upon the uneven moisture content created in the grain after theoriginal drying. If the drying time is adjusted to obtain a certain meanmoisture ratio in the discharged grain, the moisture ratio at the grainsurface will be considerably below that value due to the delay-caused bythe quick-dryingin the movement of the moisture from the inner portionof the grain and out to the surface of the same. As a consequence, themoisture ratio in the surface layer will often be below the hygroscopicequilibrium state of the outdoor air, and the grain therefore during thefirst part of the cooling absorbs moisture from the cooling air. Besidesthe disadvantage of an undesirable moistening of the grain there will bea surplus of heat resulting from the heat of condensation which prolongsthe required cooling period. The super-dried surface layer will alsoprevent the outward movement of the moisture from the inner portionwhich is necessary for the moisture equalization, said moisture movementfurthermore being delayed by a reduction of the temperature of thegrain. Because of this prevention of the equalization of the moisture tothe desired extent, the heat transmission necessary for the cooling iseffected entirely by means of convection.

The method according to the invention is characterized by the fact thatthe material between the treatment steps is continuously transmitted toan equalizing zone, where the material is substantially isolated fromthe influence of the treatment medium.

Owing to the fact that the moisture equalization in the grain in thismanner is performed at a fixed high temperature, the moisture movementwill take place quicker and the grain will enter the cooling zone withso high a moisture ratio in the surface layer, that there is no risk ofwater absorption. Another object of the invention is a dividing, ifdesired, of the drying into two steps by providing a similar equalizingzone between the steps.

The invention also relates to a device for performing the method. Such adevice consists of a unit in form of a rectangular box and equipped withinlet and outlet openings at opposite ends for the material to betreated and equipped with a substantially horizontal, perforatedintermediate bottom wall, functioning as a supporting plane for thematerial, and one or more ventilators connected to the space below theintermediate bottom wall for supplying treatment medium and a dischargeopening for this medium arranged above the intermediate bottom wall. Asuitable embodiment of the device is characterized in that thesupporting plane in the equalizing zone or zones is made withoutperforations or with perforations providing a considerably reduced flowarea. According to another embodiment the space below the supportingplane is equipped with partitions at opposite ends of each equalizingzone and the equalizing zones are connected to supply means for atreatment medium of considerably lower pressure than that of thetreatment zones. In sections where no air is blown through the grainparticles, or at such a low velocity of the medium that fluidizationdoes not take place, the conveyance of the material can be efiected byvibrating or shaking the supporting plane or by a scraping conveyor.

According to one embodiment, the device for performing the methodaccording to the invention may consist of two or more units arranged oneabove the other and of equal dimensions, but a mirror image of eachother and shaped as rectangular boxes. Each unit is equipped with inletand outlet openings at opposite ends for the material to be treated andis provided with a horizontal, perforated intermediate bottom wallfunctioning as a supporting plane for the material, a ventilatorconnected to the space below the intermediate bottom wall for supplyingtreatment medium, and a discharge opening above the intermediate bottomwall for this medium. A characteristic feature of this embodiment isthat the perforated intermediate bottom wall terminates some distancefrom the outlet end of its associated unit in a depending verticalpartition, which defines a shaft-like space ending in the outlet openingfor the material, said opening being arranged in the bottom of the unit.

According to all of the above mentioned embodiments of the device, theoutlet for the discharged treatment medium can suitablyin order toprevent the grain from being caught by the descending treatmentmedium-be made as a slot in one or both of the side walls and have thesame length as the perforated intermediate bottom wall. The slotterminates in an outlet duct arranged at the outer side of the unithaving the same length as the slot and having a how area of about oneand a half times as large as said slot. The outlet duct has anupwardlyfacing outlet opening which is defined by an inwardly bent edge,functioning as a catching rim. The side wall of the unit along the loweredge of said slot is formed with a V-shaped inwardly bent marginalportion or deflector for deflecting the material.

The invention will now be described more in detail with reference to theaccompanying drawings, which show suitable embodiments of the devicesfor performing the method wherein:

FIG. 1 shows a vertical longitudinal section of an embodiment of thedevice.

FIG. 2 shows a cross section through the device along the section line2--2 in FIG. 1.

FIG. 3 shows a vertical longitudinal section of another embodiment ofthe device.

FIG. 4- shows a cross section through the last mentioned embodiment ofthe device along the section line 44 of FIG. 3.

FIG. 5 shows a vertical longitudinal section through a modifiedembodiment of the device.

FIG. 6 shows a cross section through this modified embodiment along thesection line 6-6 in FIG. 5.

FIG. 7 shows a plan view of the last mentioned device.

FIG. 8 is a fragmentary longitudinal vertical section showing amodification of the apparatus illustrated in FIGS. 1 and 2.

In the drawing, and more particularly FIGS. 1 and 2, the dryer comprisesa rectangular box 1 formed as a unit with end wall 2 and 2a, a bottom 7and a roof 6 of sheet metal. The unit is provided with an inlet opening3, made in the roof near the end wall 2 and an outlet opening 12 in thebottom of the section near the opposite end wall 2a. In the unit thereis arranged a perforated intermediate bottom wall 8, supporting thematerial 9 to be dried and at the same time functioning as adistributing device for the treatment medium. A partition 28 dependsfrom the intermediate bottom wall 8 at its end adjacent the end wall 2ato define therebetween the outlet opening 12. The material to be dried,i.e. the grain, is fed from a feeding hopper 4 and the feed of materialis governed by means of an adjustable partition 5, in order to obtain asuitable layer of material 9. The space 16 below the perforatedinter-mediate bottom 3 is connected'through a heater'Zt) to a ventilator21 supplying the treatment medium.

According to the invention the intermediate bottom.

wall 8 is provided with ordinary perforations in the section A, whilethe bottom wall in the section B is provided with only smallperforations to provide diminished'flow' of medium through the material9 in this section. if

desired, the bottom wall in the section'B may be imperforate as shown at8a in FIG. 8 to provide the diminished flow. discharge which functionsas cooling zone, the intermediate bottom wall is provided with ordinaryperforations.

'From the cooling zone the grain is emptied into an outlet trough 16through the opening 12, from where the grain can be conveyed by means ofan elevator 13, a

not take place, the conveyance of the grain can be ef fected by ascraping conveyor shown schematically at 29 t in FIGS. 1 and 2, or byvibrating the supporting plane for example by a vibrator shown at 29a inFIG. 8.

For the discharge of the treatment medium there are slot-shaped openings11 of the same length as the per forated intermediate bottom arranged inthe side walls of the section. The slot can be made with constant widthas shown, or-for the purpose of an even distribution of medium-withvarying width. The slot 11 terminates in an outlet duct 22 arranged onthe outer side of the unit. one and a half times the flow area of theslot 11. The duct has along its top an outlet opening 24, defined by aninwardly bent edge 23 functioning as a'catching rim for catching grainparticles, if any. Likewise, in order to prevent the grain from beingcaught by the discharged medium the side wall is along the lower edge ofthe slot provided with a V-shaped inwardly bent deflector 25 "fordeflecting the material. In most 'cases it is sufiicient touse onesingle slot 'and an 'outlet'duct for the discharge of the treatmentmedium. The outlet duct of similar form at the other side of the unitcan in such a case, as 1 shown in FIG. 2, be provided with a small door26' which may be fo pened for inspection and testing of the material.For heating the treatment medium used in the drying zone in the caseshown in 1, the ventilator '21 is connected to the chamber 10'throughthe heating coil 26 for heating by means of steam or hotwater.Airis supplied to the cooling zone either from a In the section C of thedevice next to the- The flow area of the duct 22 is preferably 49 in theupper unit 41a.

separate ventilator or, as in the case shown, from the same ventilator21 through a by-pass 1S, equipped with an adjusting damper 19. Apartition 17 is mounted in the space 10 for separating the drying andcooling mediums.

The embodiment of the device shown in FIG. 3 differs from that shown inFIG. 1 in that the space lfia below the supporting plane is providedwith partitions 17a and 17b at opposite sides of the equalizing zone B.Furthermore, in this case the equalizing zones are connected to separatesupplying means 21b for a treating medium of considerably lower pressurethan in the treatment zones A, C to which treating medium is supplied bymeans of the ventilators 21a and 21c.' Tht supplying means 21b is in thecase shown connected to the equalizing zone by means of a duct 27%), inwhich can be inserted a heating coil 28b. In similar manner a heating.coil 29a can be arranged in the duct 7a from the supplying means 21a tothe treatment zone A. A duct 27c connects the supply means 210 to thecooling zone C.

In the device illustrated in FIG; 5 there are two closed super-imposedunits 41a and 41b in form of rectangular boxes of equal dimensions, thesecond unit, however, being the mirror image of the first one.

The upper unit 41a has end walls 42 and 42a, a bottom 47, and a roof 46.The unit is provided with an inlet opening 43 near the end wall 42which'is fed from a. feeding hopper 4-4. The feed of material isgoverned by an adjustable partition 45 to provide a suitable layer offluidized material 49. A perforated bottom wall 48 is spaced upwardlyfrom the bottom 47 to define therea heater 60 to a ventilator 51. Heatedmedium is thus supplied to the chamber 50 and passes upwardly throughthe perforated bottom Wall 48 to fluidize the material To discharge thetreatment medium from above the material 49, openings 61 are formed inthe side walls of the unit. The openings 61 may be of constant width,or, as shown, to provide an even distribution of medium with varyingwidths. The outlet opening 64 is similar to the opening 24 and need notbe described further. The intermediate bottom wall 48 terminates at itsend adjacent the end wall 42a in a depending partition 53'which definesan outlet 52from the upper unit 4-1a'between the partition 53 and theend wall 42a. The partition extends downwardly into the unit 41b to forma shaft-like space or chamber 54 isolated from the, treatment medium.The upper end of the chamber 54 forms the discharge opening for theupper unit 41a, and the lower end of the chamber 54 forms the inletopening to the unit 41b. The sides of the inlet opening 55 is controlledby an adjustable partition 45b to determine the level of the material491; in the lower unit. The lower unit has an' intermediate bottom wall48b which defines a space 5% therebelow supplied with cooling medium bya ventilator 51b. The cooling supplied through the perforated Wall 48bpasses upwardly through the material 4% and is discharged through aslot'61b and discharge openings 6% (FIG. 6) similarin con struction tothe discharge opening 64. The perforated wall 48b terminates adjacentthe reniote'end wall 42b of the lower unit 415 in a depending partition53b which defines an outlet opening 52b from which the material isremoved similarly to'themanner illustratedand describedinconnection'with the embodiment illustratedin FIGS; 1 and Z. a

In this "embodiment said space 54 constitutes a resting space 54.should: suitably be dimensioned so that the equalizing time correspondsto at least of the drying time.

In this embodiment the heating coil 60 is as illustrated in FIG. 7arranged on the suction side of the ventilator. This heating coil mayalso be substituted by a heat exchanger for indirect heating by means offlue gases or the necessary heat may also be supplied by direct additionof flue gases to the supplied out-door air. In order to increase theheat economy, part of the treating medium may be recirculated. Thedischarge duct of the treating medium may be recirculated. The dischargeduct 62 is in such cases, as illustrated in FIG. 7 connected with theheating coil or the inlet of the ventilator by means of a duct 65,provided with a damper regulated inlet 66 for outdoor air. In order tomake it possible to separate impurities accompanying the medium saidreturn connection is suitably passing a dust settling chamber 67.

What we claim is:

A method of treating granular materials which comprises the steps ofintroducing the material into a first bed in a drying zone, passing astream of drying medium up through the bottom of said first bed tofluidize the material therein, whereby said material is subjected tosaid drying medium for a predetermined time period, continuouslywithdrawing the dried material front one end of said first bed andintroducing the material into an equalizing zone, interrupting thefluidization of the material in the equalizing zone by keeping thematerial in said equalizing zone substantially isolated from the effectoftreatment medium for a second predetermined time period at least onefourth said first predetermined time period to render the moisturecontent of the material uniform throughout, and then introducing thematerial from said zone into a second bed in a cooling zone, passing astream of cooling medium upwardly through the bottom of said second bedto fluidize the material therein while cooling the same, andcontinuously withdrawing the cooled material from said second bed.

References Cited in the file of this patent UNITED STATES PATENTS2,371,619 Hartley Mar. 20, 1945 2,582,688 Ford Jan. 15, 1952 2,635,684Joscelyne Apr. 21, 1953 2,676,668 Lindsay Apr. 27, 1954 2,702,434Richardson et al Feb. 22, 1955 2,715,282 Niven Aug. 16, 1955 2,797,908Zubrzycki July 2, 1957

